Objective: The specific aims of this project are to study the normal synaptic organization within the nature and developing spinal trigeminal nucleus and olfactory cortex of rats and cats and to define and characterize the morphological effects of specific lesion producing synaptic degeneration and deafferentation of these structures. Light and electron microscopic methods will be used primarily for qualitative and quantitative evaluations of synaptic structures during development, in the mature state, and during the sequence of degenerative changes resulting in chronic deafferentation. Special emphasis will be directed toward obtaining reproducable preparations of the greatest possible primary deafferentation of a particular region; quantification and characterization of persisting, possibly modified, synaptic structures; evaluation of enzymatic activity at degenerating terminals and postsynaptic regions; and testing the possibility of reestablishment of synapses or synaptic reorganization caused by this deafferentation in both mature and newborn animals. The fine structure of developing synaptic profiles, their changes with deafferentating lesions and the effect on resultant axon patterns following primary deafferentation at various stages of maturation of these synaptic structures are the parts of the project receiving major emphasis currently.